Dual emission via remote control of molecular rotation of o-carborane in the excited state by the distant substituents in tolane-modified dyads

Abstract

Dual-emissive properties and their environment responsiveness are reported based on the tolane-o-carborane dyad having various substituents at the tolane moiety. A series of o-carborane dyads were synthesized and characterized. It was shown that their luminescent colors were tuned by the substituents at the tolane moiety. Some derivatives with strong electron-donating substituents such as –OMe, –(OMe)₃ and –NMe₂ simultaneously showed dual emission bands from the locally-excited (LE) state in the parallel conformation and an intramolecular charge transfer (ICT) state in the twisted one in the octane solution. Furthermore, intensity ratios between two emission bands were varied by heating. These results mean that the electronic properties of the o-carborane dyad system can be modulated by the degree of electron donating properties at the substituents via electronic conjugation.